Identifying novel endogenous ligands that promote thrombosis and inflammatory processes in pathological settings, such as, diabetes, hypercholesterolemia and vascular hypertension may lead to new therapies that improve outcomes in patients at high risk for stroke. A variant of fibronectin (FN) containing the alternatively-spliced extra domain A (EDA+-FN), which is absent in the arteries or circulation of healthy humans and mice, is specifically expressed in the endothelium of atherosclerotic arteries and elevated in circulation during pathological settings, such as diabetes, atherosclerosis and vascular hypertension, most likely due to endothelial dysfunction. Recently, we have discovered that EDA+-FN promotes thrombosis and inflammatory processes. The underlying mechanisms by which EDA+-FN contributes to thrombosis and inflammation are not well understood. EDA+-FN is known to activate the toll-like- receptor 4 (TLR4) signaling pathway. Additionally, EDA is a ligand for integrin 91, which is expressed on inflammatory cells, such as, neutrophils and macrophages. Hypercholesterolemia is one of the major risk factors for acute stroke in humans. Therefore, in hypercholesterolemic apolipoprotein E-deficient (ApoE-/-, atherosclerosis prone) mice, we propose to test the central hypothesis that EDA+-FN contributes to ischemia/reperfusion (I/R) brain injury in pathological setting, and that it does so by enhancing thrombosis and inflammatory processes via parallel 91and TLR4-mediated pathways. In Aim1, we will define the role of TLR4 in EDA+-FN-mediated thrombosis and inflammatory I/R brain injury. In Aim 2, we will determine the role of integrin 91 in EDA+-FN -mediated thrombosis and inflammatory I/R brain injury. In Aim 3, we will define the role of plasma versus endothelial cell EDA+-FN in I/R brain injury. Furthermore, we will determine the source of EDA+-FN in the plasma of the aforementioned pathological conditions. As a translational approach, we will test the hypothesis that blocking EDA+-FN with specific monoclonal antibodies will reduce stroke injury in the context of hypercholesterolemia. To achieve our specific experimental goals, we have developed novel genetically modified mice strains and reagents that we will share with other researchers in the field. The contribution of th proposed studies is highly clinically significant as it determine the mechanistic insights by which EDA+-FN promotes thrombosis and inflammatory brain injury in disease context of atherosclerosis. The proposal has future translational potential, as it may have significant impact on the diagnosis and treatment of common thrombo-inflammatory diseases including acute stroke.